Prosthetic foot with modular construction

ABSTRACT

A prosthetic foot includes a heel member having a heel member shaft extending upwardly from a heel end thereof and a forefoot member having a forefoot member shaft extending upwardly from a toe end thereof. An ankle member receives the heel member shaft and forefoot member shaft so as to allow the heel member shaft and forefoot member shaft to translate in a direction of a wearer&#39;s leg in response to an upward force thereon. At least one compressible member is coupled to the ankle member and is in compressible contact with the heel member shaft and/or forefoot member shaft so as to compress in response to the translation thereof.

CROSS-REFERENCE TO RELATED APPLICATIONS

This claims priority to U.S. provisional application 61/712,981, filedOct. 12, 2012 and titled “Prosthetic Foot with InterchangeableComponents,” which is incorporated by reference in its entirety.

FIELD OF THE INVENTION

The invention relates to prosthetic feet and, more particularly, toprosthetic feet made of interchangeable components.

BACKGROUND

Amputees that wear a prosthetic foot to enhance their mobility mustchoose a prosthetic foot that is appropriate for their size andlifestyle. Unfortunately, prosthetic feet that are designed forday-to-day activities such as walking are not ideal for performingvigorous exercise. For this reason, many amputees will have differentprosthetic feet for different activities. In order to change between thedifferent prosthetic feet when using conventional prosthetics, theamputee must completely remove the foot attached to the leg and replaceit with a different foot. This is inefficient, expensive, and may changegait adjustments originally set by the attending prosthetist.

Conventional prosthetic feet are usually made of a plurality ofcomponents that are fastened together mechanically or with an adhesiveto form a single structure. These are not designed to allow the wearerto replace different components, nor are they engineered to allow theamputee to replace, for example, walking foot components with runningfoot components without replacing the entire foot.

SUMMARY

In view of these problems, we have developed a prosthetic foot designedso that its components can easily be removed and replaced. The footeffectively allows wearers to have a single prosthetic foot that isadaptable to many different activities and sizes by selectinginterchangeable components.

A first example of a prosthetic foot embodying these principlescomprises a heel member having a heel member shaft extending upwardlyfrom a heel end thereof and a forefoot member having a forefoot membershaft extending upwardly from a toe end thereof. An ankle memberreceives the heel member shaft and forefoot member shaft therein so asto allow the heel member shaft and forefoot member shaft to translate ina direction of a wearer's leg in response to an upward force thereon. Atleast one compressible member is coupled to the ankle member and incompressible contact with the heel member shaft and/or forefoot membershaft so as to compress in response to the translation of the heelmember shaft and/or forefoot member shaft.

Other features of this first example may include the following.

The ankle member may apply inward force to the heel member shaft andforefoot member shaft to maintain an alignment of the heel member shaftand forefoot member shaft therealong.

The heel member shaft and forefoot member shaft may be translatablealong the ankle member independently of one another.

The ankle member may form a sleeve around the heel member shaft andforefoot member shaft and the heel member shaft and forefoot membershaft may translate upwardly within the sleeve when upward force acts,respectively, on the heel member or forefoot member. In this case, thecompressible member may be positioned above the heel member shaft andforefoot member shaft within the sleeve.

The ankle member may apply inward force to the compressible member whenthe compressible member is compressed to maintain the compressiblemember's alignment with the heel member shaft and forefoot member shaft.

The heel member shaft and forefoot member shaft may translate upwardlyalong the ankle member along or more guide slots defining the directionof translation, each guide slot having a corresponding pin insertedtherein to restrict translation within a length of the one or more guideslots.

A second example of a prosthetic foot embodying these principlescomprises an ankle member having a sleeve defining an interior extendingalong an axis defined by a wearer's leg and having a compressible memberpositioned therein; a heel member having a heel member shaft extendingupwardly from a heel end thereof and along the axis within the interior;a forefoot member having a forefoot member shaft extending upwardly froma toe end and along the axis within the interior. The heel member shaftand forefoot member shaft are translatable along the axis in response toan upward force thereon. The compressible member compresses in responseto the upward force.

Other features of the second example may include the following.

The ankle member may apply inward force to the heel member shaft andforefoot member shaft to maintain alignment of the heel member shaft andforefoot member shaft therealong.

The heel member shaft and forefoot member shaft may be translatablealong the axis independently of one another.

The compressible member may be positioned above the heel member shaftand forefoot member shaft and intersect the axis.

The ankle member may apply inward force to the compressible member whenthe compressible member is compressed to maintain the compressiblemember's alignment with the heel member shaft and forefoot member shaft.

The extent of translatability may be defined by one more guide slotswithin the sleeve, extending along the axis, and having a correspondingpin inserted therein.

A third example of a prosthetic foot embodying these principlescomprises an ankle member having a sleeve defining an interior extendingalong an axis defined by a wearer's leg, the interior being at leastpartially defined by anterior and posterior lubricated sidewalls; a heelmember having a heel member shaft within the sleeve, a heel endextending downwardly out of the sleeve, and opposed lubricated anteriorand posterior heel member surfaces, the lubricated posterior heel membersurface being in slidable contact with the ankle member posteriorlubricated sidewall; a forefoot member having a forefoot member shaftwithin the sleeve, a toe end extending downwardly and forwardly out ofthe sleeve, and opposed lubricated anterior and posterior forefootmember surfaces, the lubricated anterior forefoot member surface beingin slidable contact with the ankle member anterior lubricated sidewall,the lubricated posterior forefoot member surface being in slidablecontact with the lubricated anterior heel member surface; and acompressible member positioned within the interior above and in contactwith the heel member shaft and forefoot member shaft so as to compresswhen upward force acts on the heel member and/or forefoot member.

Other features of the third example may include the following.

The heel member shaft and forefoot member shaft may together define apair of opposed guide slots, each having a pin inserted therein torestrict the movement of the heel member and forefoot member to a lengthof the guide slots.

The pins may extend through opposed lateral sidewalls of the anklemember.

A pin securing member may apply inward force against the pins tomaintain the pins within the guide slots.

The ankle member may apply inward force to the compressible member whenthe compressible member is compressed to maintain the compressiblemember's alignment with the heel member shaft and forefoot member shaft.

These and other objects, aspects, and advantages of the invention willbe better appreciated in view of the following detailed description ofpreferred embodiments.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side anterior perspective view of a prosthetic footconnected to a limb connector, according to an embodiment of theinvention;

FIG. 2 is a side view thereof with a lateral side of the ankle membercutaway;

FIG. 3 is a front view thereof with the anterior side of the anklemember cutaway;

FIG. 4 is a side anterior perspective view of an exemplary forefootmember useful with the prosthetic foot of FIG. 1;

FIG. 5 is a side elevation of the forefoot member of FIG. 4;

FIG. 6 is a bottom view of the forefoot member of FIG. 4;

FIG. 7 is an anterior elevation view of the forefoot member of FIG. 4;

FIG. 8 is a posterior elevation view of the forefoot member of FIG. 4;

FIG. 9 is a side posterior perspective view of an exemplary heel memberuseful with the prosthetic foot of FIG. 1;

FIG. 10 is a side elevation view of the heel member of FIG. 9;

FIG. 11 is a bottom view of the heel member of FIG. 9;

FIG. 12 is a posterior elevation view of the heel member of FIG. 9;

FIG. 13 is an anterior elevation view of the heel member of FIG. 9;

FIG. 14 is a bottom perspective view of an exemplary ankle member usefulwith the prosthetic foot of FIG. 1;

FIG. 15 is a bottom view of the ankle member of FIG. 14;

FIG. 16 is anterior or posterior side elevation view of the ankle memberof FIG. 14 with the facing side cutaway;

FIG. 17 is a lateral side elevation view of the ankle member of FIG. 14with the facing side cutaway;

FIG. 18 is a top view of the of an exemplary compressible member usefulwith the prosthetic foot of FIG. 1;

FIG. 19 is a side elevation view of the compressible member of FIG. 18;

FIG. 20 is a side elevation view of an exemplary pin useful with theprosthetic foot of FIG. 1;

FIG. 21 is a top or bottom view of the pin of FIG. 20;

FIG. 22 is a rear elevation view of the pin of FIG. 20;

FIG. 23 is a front elevation view of the pin of FIG. 20;

FIGS. 24A-C illustrate an example of how components of the prostheticfoot of FIG. 1 can be interchanged; and

FIG. 25 is a side anterior perspective view of the prosthetic foot ofFIG. 1 including a pin securing member.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

In the Summary above and in the Detailed Description of PreferredEmbodiments, reference is made to particular features (including methodsteps) of the invention. Where a particular feature is disclosed in thecontext of a particular aspect or embodiment of the invention, thatfeature can also be used, to the extent possible, in combination withand/or in the context of other particular aspects and embodiments of theinvention, and in the invention generally.

The term “comprises” is-used herein to mean that other ingredients,features, steps, etc. are optionally present. When reference is madeherein to a method comprising two or more defined steps, the steps canbe carried in any order or simultaneously (except where the contextexcludes that possibility), and the method can include one or more stepswhich are carried out before any of the defined steps, between two ofthe defined steps, or after all of the defined steps (except where thecontext excludes that possibility).

In this section, the invention will be described more fully withreference to certain preferred embodiments. This invention may, however,be embodied in many different forms and should not be construed aslimited to the embodiments set forth herein. Rather, these embodimentsare provided so that this disclosure will convey preferred embodimentsof the invention to those skilled in the art.

FIG. 1 generally illustrates a prosthetic foot 20 according to anembodiment of the invention. The foot 20 includes a forefoot member 30,a heel member 60, and an ankle member 90. In practice, the foot 20 isattached to a limb connector 130 designed to connect the foot to thewearer's leg. The wearer's leg defines a vertical axis L along which theankle member 90 is aligned. The limb connector 130 is shown in brokenlines to indicate that its design does not form a key component of thefoot 20. The foot 20 may function regardless of the type of limbconnector 130 used.

The prosthetic foot 20 is modular and includes parts that can be removedand substituted very easily to meet the individual needs of the wearer.This allows the components to be interchanged with other components forthe purpose of replacement or for the purpose of substituting onecomponent for another component having different properties. Forexample, the original forefoot and heel members may be interchanged withdifferent forefoot and heel members suited to a particular activity, thewearer's gait, the wearer's lifestyle, a particular shoe size, thewearer's height, the wearer's weight.

In FIGS. 2 and 3 the facing side of the ankle member 90 is cutaway sothat the mechanical functionality of various components is revealed. Thedetails of each component are discussed in turn.

The ankle member 90 forms a sleeve into which a forefoot member shaft 32and heel member shaft 62 are positioned. The ankle member 90 appliesinward force against the forefoot member shaft 32 and heel member shaft62 to maintain alignment of the respective shafts 32, 62 along thevertical axis of the ankle member 90. The forefoot member shaft 32 andheel member shaft 62 slide independently along the ankle member whenupward force acts on the forefoot member 30 or heel member 60.

A compressible member 110 is coupled to the ankle member 90 and is incompressible contact with the heel member shaft 62 and forefoot membershaft 32 so as to compress when upward force acts on the heel member 60and/or forefoot member 30. The vertical arrow A in FIGS. 2 and 3illustrates that the compressible member 110 compresses along thedirection of the vertical axis of the ankle member 90. The verticalarrows B and C illustrate the direction the shafts 32, 62 slide alongthe ankle member 90.

When upward force acts on the heel member 60 or forefoot member 30, therespective shaft 32, 62 slides vertically within the ankle member 90 andcompresses the compressible member 110, which absorbs the shock due tothe force. The heel member shaft 62 and forefoot member shaft 32 slideindependently of one another along the ankle member 90 because the onlymechanical link between the shafts 32, 62 is the inward force applied byankle member 90.

The heel member 60 can easily be removed from the ankle member 90 bysliding it out of the ankle member 90. Likewise, the forefoot member 32can easily be removed from the ankle member 90 by sliding it out of theankle member 90. Either of these components can then be replaced with adifferent heel member 60 and/or forefoot member 30 that suits a certainactivity or weight without needing to remove the ankle member 90 fromthe wearer's limb. This also allows worn components to be replacedwithout needing to replace the entire foot or send the foot back to themanufacturer for repair.

Additional details of a preferred forefoot member 30 are shown in FIGS.4-8. The forefoot member 30 includes the forefoot member shaft 32 andextends from a forefoot member upper end 34 through a curved forefootsection 36 to a toe section end 38 and terminates at a toe end 40. Aforefoot member top surface 42 and forefoot member bottom surface 44 arepositioned on opposite sides.

At the shaft section 32, the forefoot member top surface 42 includes alubricated forefoot member anterior surface 46. Also at the shaftsection 32, the forefoot member bottom surface 44 includes a lubricatedforefoot member posterior surface 48.

The opposed lateral sides of the forefoot member each include anelongated depression 50 formed along the shaft 32 adjacent to thelubricated forefoot member posterior surface 48.

Additional details of a preferred heel member 60 are shown in FIGS.9-13. The heel member 60 includes the heel member shaft 62 and extendsfrom a heel member upper end 64 through a curved heel section 72 to aheel end 66. A heel member top surface 68 and heel member bottom surface70 are positioned on opposite sides.

At the shaft section 62, the heel member top surface 68 includes alubricated heel member posterior surface 74. Also at the shaft section62, the heel member bottom surface 70 includes a lubricated heel memberanterior surface 76.

The opposed lateral sides of the heel member 60 each include anelongated depression 78 formed along the shaft 62 adjacent to thelubricated heel member anterior surface 76.

Additional details of a preferred ankle member 90 are shown in FIGS.14-17. The ankle member 90 forms a sleeve having opposed anterior andposterior sidewalls 92 a and opposed lateral side walls 92 b thattogether define an interior 100. The interior surface along the anteriorand posterior sidewalls 92 a is lubricated to form anterior andposterior lubricated sidewalls 104. In the embodiment shown, the anklemember 90 is symmetric about a vertical plane bisecting the anterior andposterior sidewalls 92 a and a vertical plane bisecting the lateral sidewalls 92 b.

Both lateral sidewalls 92 b define a respective opening 102 that passesthrough to the interior 100. The purpose of the openings 102 isdescribed in detail below.

Additional details of the preferred compressible member 110 are shown inFIGS. 18 and 19. The compressible member 110 is adapted to compress inthe vertical direction and return to its original shape when thecompression force is removed. Accordingly, the compressible member 110functions in a spring-like manner to absorb the shock on the heel member60 and forefoot member 30 when the wearer uses the prosthetic foot.

In the example shown, the compressible member 110 forms an elongateddisk-like shape with a compressible material 112 in a high flexure andfatigue resistant material sheath 114. The compressible material 112 ispreferably rubber, plastic, or the like. The sheath 114 is preferablyalso rubber, plastic, or the like. The make up of the compressiblematerial 112 is specifically selected for the degree of energy recoveryrequired to match the wearer's lifestyle and body weight. The materialproperty combinations for the compressible material 112 material andsheath 114 determine the energy recovery performance of the compressiblemember 110. These materials may be selected to provide a specific typeof shock-absorbing performance tuned to a wearer's preference.

When the compressible member 110 compresses, it recovers energy from theheel member 60 and forefoot member 30 and returns a significant amountof that energy back to the heel member 60 and forefoot member 30 toallow the wearer to have a more natural stride. The compressible member110 also returns rapid shock induced energy, from jumping for example,in a controlled manner. If the compressible member 110 becomesoverloaded or fatigued and the sheath 114 fails, the compressible member110 will not totally fail because the compressible material 112 willremain intact.

The shape of the compressible member 110 is selected to fit within theinterior 100 of the ankle member 90 so that when the compressible member110 is compressed, it deforms and presses against the interior sidewalls92 a,b of the ankle member, which, in turn, maintain its alignment withthe forefoot member 30 and heel member 60. For this reason, it ispreferred that the height H, width W, and thickness T of thecompressible member 110 be such that it fits snugly within the anklemember 90 so that the ankle member's interior walls either touch it ornearly touch it when the compressible member 110 is not compressed. Thepreferred arrangement of the compressible member 110 with respect to theankle member 90 is best shown in FIGS. 2 and 3. The shape of thecompressible member 110 can be altered to correspond to the shape of theinterior 100 of the ankle member 90. Accordingly, the compressiblemember 110 need not have the shape shown in every embodiment.

Limiting the lateral expansion of the compressible member 110 within theankle member 90 is advantageous for many reasons, which includepreventing destructive overstressing of the sheath 114 and changing thewearer's “feel” while walking to identify the need to replace thecompressible member 110.

Although the compressible member 110 shown in the drawings and describedhere is particularly preferred, the compressible member 110 is notlimited to this specific example. There are various other types ofspring-like or shock absorbing devices that one having skill in the art,using this disclosure as guidance, may use to serve the same purpose.

Referring back now to FIG. 2, when the forefoot member 30 and heelmember 60 are coupled to the ankle member 90 the lubricated posteriorheel member surface 74 is in slidable contact with the ankle memberposterior lubricated sidewall 104, the lubricated anterior forefootmember surface 46 is in slidable contact with the ankle member anteriorlubricated sidewall 104, and the lubricated posterior forefoot membersurface 48 is in slidable contact with the lubricated anterior heelmember surface 76.

The lubricated surfaces are preferably formed from a solid lubricatingmaterial inlaid into the material that makes up the respective componentpart. The lubricating material allows the surfaces to slide quietlyagainst each other with little wear. A particularly preferredlubricating material is polytetrafluoroethylene, commonly sold under thename TEFLON® by E.I. DuPont de Nemours and Company, Corp. Other suitablelubricating materials include, but are not limited toother families offluoropolymers, polyethylene polymers of various molecular weights,acetal resins (commonly sold under the name DELRIN®, by E.I. DuPont deNemours and Company, Corp), or any other polymer that has goodresistance to wear due to sliding.

Although not preferable, if desired, a liquid or gel-type lubricant canbe applied to the lubricated surfaces for extra lubrication. One must becareful, however, in choosing the lubricant because grit trapped in thelubricant may damage the solid lubricating material.

As shown in FIGS. 1 and 2, pins 120 are positioned through the opposedlateral sidewalls 92 b of the ankle member 90. Preferred pins 120 areshown in greater detail in FIGS. 20-23. Each pin 120 includes acylindrical body 122 extending from a first end 123 to a wedge shapedsecond end 124. The pins 120 are preferably made from the samelubricating material as the lubricated surfaces, most preferablypolytetrafluoroethylene, to allow the wedge shaped second end 124 toslide easily against the heel member 90 and forefoot member 30.

As best shown in FIGS. 2 and 24A-C, within the ankle member 90, therespective depressions 50, 78 of the forefoot member 30 and heel member60 meet to form a pair of vertical guide slots that define the slidingdirection in which the forefoot member 30 and heel member 60 slide. Asbest shown in FIG. 3, the pins 120 are positioned through the openings102 in the ankle member 90 so that the wedge shaped second end 124 ofeach pin 102 fits within a respective guide slot. The pins 120 restrictthe distance the forefoot member 30 and heel member 90 can slide to thelength of the guide slots.

As mentioned above, the various components of the prosthetic foot 20 caneasily be removed from the ankle member 90 without removing the anklemember 90 from the wearer's leg. This is advantageous for many reasons,some of which have already been described.

One of the particular advantages of the foot's modularity is that isallows one to easily replace the heel member 60 and forefoot member 30.An example of this is illustrated in FIGS. 24A-C in which a height ofthe heel end above ground G is adjusted by replacing heel member 60′with shorter heel member 60′″. This is achieved by sliding heel member60′ out of the ankle member 90 and sliding heel member 60″into the anklemember 90 as illustrated by the arrows in FIG. 24B. The guide pins (notshown) are installed as previously described. FIG. 24C shows the shorterheel member 60″installed on the prosthetic foot 20.

Referring now to FIG. 25, it may be useful to include a pin securingmember 140 to maintain the position of the pins 120. In the exampleshown, the pin securing member 140 is an annular strap that extendscompletely around the ankle member 90 and presses inwardly on the pins120. There many different strap-type pin securing members 140 that aresuitable, including resilient straps that can be stretched over the pins120 or belt-like straps that include a fastener for joining two endstogether. A preferred pin securing member 140 is a belt-like strap witha hook and loop type fastener. When used, the pin securing member 140 ispreferably tightened around the pins 120 to prevent the pins fromsliding out of the openings 102 while pressing the second end 124 of thepins 120 into the guide slots, which, in turn, causes the anteriorlubricious surface 46 of the forefoot member and the posteriorlubricious surface 74 of the heel member 90 to press against thelubricious surfaces 104 on the interior of the ankle member 90.

The prosthetic foot 20 may be made from any material suitable for makingcomponents parts of prosthetic devices and that can allow each of thecomponents to perform its desired functions. The forefoot member 30,heel member 60, and ankle member 90 may be primarily made of the same ora different material. A particularly preferred material for making theforefoot member 30, heel member 60, and ankle member 90 is carbon fibercomposite because it is lightweight, strong, and resilient. Theproperties of carbon fiber are also tunable to meet a desired need byvarying the ply schedule, layer orientation, resins, and fabricationprocess employed to make each part.

The scope of the invention is not limited to the particular shape of thecomponent shown in the drawings and described. The shape of eachcomponent may vary to account for a wearer's activity level and/orweight or may vary to be suited to a particular activity such asrunning.

The invention has been described in some detail, but it will be apparentthat various modifications and changes can be made within the spirit andscope of the invention as described in the foregoing specification andthe appended claims.

1. (canceled)
 2. (canceled)
 3. A prosthetic foot comprising: a heelmember having a heel member shaft extending upwardly from a heel endthereof; a forefoot member having a forefoot member shaft extendingupwardly from a toe end thereof; an ankle member receiving the heelmember shaft and forefoot member shaft therein so as to allow the heelmember shaft and forefoot member shaft to translate in a direction of awearer's leg in response to an upward force thereon; and at least onecompressible member coupled to the ankle member and in compressiblecontact with the heel member shaft and/or forefoot member shaft so as tocompress in response to the translation thereof; wherein the heel membershaft and forefoot member shaft are translatable along the ankle memberindependently of one another.
 4. The prosthetic foot of claim 3, whereinthe ankle member forms a sleeve around the heel member shaft andforefoot member shaft and the heel member shaft and forefoot membershaft translate upwardly within the sleeve when upward force acts,respectively, on the heel member or forefoot member.
 5. The prostheticfoot of claim 4, wherein the compressible member is positioned above theheel member shaft and forefoot member shaft within the sleeve.
 6. Theprosthetic foot of claim 4, wherein the ankle member applies inwardforce to the compressible member when the compressible member iscompressed to maintain the compressible member's alignment with the heelmember shaft and forefoot member shaft.
 7. The prosthetic foot of claim3, wherein the heel member shaft and forefoot member shaft translateupwardly along the ankle member along or more guide slots defining thedirection of translation, each guide slot having a corresponding pininserted therein to restrict translation within a length of the one ormore guide slots.
 8. (canceled)
 9. (canceled)
 10. A prosthetic footcomprising: an ankle member having a sleeve defining an interiorextending along an axis defined by a wearer's leg and having acompressible member positioned therein; a heel member having a heelmember shaft extending upwardly from a heel end thereof and along theaxis within the interior; and a forefoot member having a forefoot membershaft extending upwardly from a toe end and along the axis within theinterior; wherein the heel member shaft and forefoot member shaft aretranslatable along the axis in response to an upward force thereon andthe compressible member compresses in response to the upward force; andwherein the heel member shaft and forefoot member shaft are translatablealong the axis independently of one another.
 11. The prosthetic foot ofclaim 10, wherein the compressible member is positioned above the heelmember shaft and forefoot member shaft and intersects the axis.
 12. Theprosthetic foot of claim 11, wherein the ankle member applies inwardforce to the compressible member when the compressible member iscompressed to maintain the compressible member's alignment with the heelmember shaft and forefoot member shaft.
 13. The prosthetic foot of claim10, wherein the extent of translatability is defined by one more guideslots within the sleeve, extending along the axis, and having acorresponding pin inserted therein.
 14. A prosthetic foot comprising: anankle member having a sleeve defining an interior extending along anaxis defined by a wearer's leg, the interior being at least partiallydefined by anterior and posterior lubricated sidewalls; a heel memberhaving a heel member shaft within the sleeve, a heel end extendingdownwardly out of the sleeve, and opposed lubricated anterior andposterior heel member surfaces, the lubricated posterior heel membersurface being in slidable contact with the ankle member posteriorlubricated sidewall; a forefoot member having a forefoot member shaftwithin the sleeve, a toe end extending downwardly and forwardly out ofthe sleeve, and opposed lubricated anterior and posterior forefootmember surfaces, the lubricated anterior forefoot member surface beingin slidable contact with the ankle member anterior lubricated sidewall,the lubricated posterior forefoot member surface being in slidablecontact with the lubricated anterior heel member surface; and acompressible member positioned within the interior above and in contactwith the heel member shaft and forefoot member shaft so as to compresswhen upward force acts on the heel member and/or forefoot member. 15.The prosthetic foot of claim 14, wherein the heel member shaft andforefoot member shaft together define a pair of opposed guide slots,each having a pin inserted therein to restrict the movement of the heelmember and forefoot member to a length of the guide slots.
 16. Theprosthetic foot of claim 15, wherein the pins extend through opposedlateral sidewalls of the ankle member.
 17. The prosthetic foot of claim15, further comprising a pin securing member applying inward forceagainst the pins to maintain the pins within the guide slots.
 18. Theprosthetic foot of claim 14, wherein the ankle member applies inwardforce to the compressible member when the compressible member iscompressed to maintain the compressible member's alignment with the heelmember shaft and forefoot member shaft.